through the phloem the food is conducted
it has sieve tube elements
arrow: on attaing maturity it losses its nucleus
but we believe that all living cells must have a nucleus
though that is a living cell it doesnt have any nucleus in the adult condition
pls solve my problem

Last edited by Linn on Mon Feb 20, 2006 3:19 am, edited 1 time in total.

"How far you go in life depends on your being tender with the young, compassionate with the aged, sympathetic with the striving and tolerant of the weak and strong. Because someday in life you will have been all of these".

I also have trouble understanding this.
Only theory is that the companion cells that do have a nuclei, act
to control the seive cells.
I will do some searching on line and see what I can find.
Lynne

Poison: I dont know what you mean by RBC's?

something to do with plants?

I dont want to sound stupisd but in med terms that is red blood cells
and have no nucleous when mature so that there is more room to transport haemoglobin.
Do you mean that without nuclei the sieve tubes have more room to transport sugars?

"How far you go in life depends on your being tender with the young, compassionate with the aged, sympathetic with the striving and tolerant of the weak and strong. Because someday in life you will have been all of these".

The phloem contains sieve tubes made up of elongated cells that have lost thier nucleus and most of thier cytoplasmic organelles,. the transverse cell walls are perforated and thus ensure connection between two neighboring cells . the series of the stacked cells from a long sieve column . in addition to sieve tubes , the phloem contains companion cells next to the sieve tubes that are connected transversally with them by the plasmodesmata.Companion cells move sugars and amino acids into and out of the sieve elements.
the sieve tubes are considered to be living cells because they communicate with the companion cell that contains a nucleus, communication is done by the plasmodesmata.

but we still need a control tower somewhere to direct things.
Dont we? some cells can function w/o nuclei, but they are subject to chemical signals from other cells with nuclei?
that is what companion cells job is?

what about prokaryote cells? did I spell that right?
how do they function?

"How far you go in life depends on your being tender with the young, compassionate with the aged, sympathetic with the striving and tolerant of the weak and strong. Because someday in life you will have been all of these".

sorry Blaze
just realize basicaly same thing as you said.
communication via plasmoda

"How far you go in life depends on your being tender with the young, compassionate with the aged, sympathetic with the striving and tolerant of the weak and strong. Because someday in life you will have been all of these".